A relatively new alloy being used in aero applications is an iron-nickel-cobalt-based superalloy available from Carpenter Technology Corporation, known commercially as Thermo-Span® material, which has uniquely low thermal expansion characteristics over a broad temperature range. Thermo-Span® material offers several advantages over the mainstay alloys typically used in aero applications, making this superalloy highly attractive for various aero applications, such as, for example, for components in the high and low compressor sections of various gas turbine engines, where close control of the compressor blade and wear strip materials is required to assure compressor efficiency and stability. While this superalloy provides better corrosion resistance, improved thermal stability, good tensile properties, excellent creep resistance, and better microstructural stability as compared to traditional iron-nickel-cobalt-based controlled expansion alloys, this superalloy also has some drawbacks. Namely, Thermo-Span® material suffers from relatively poor notched mechanical properties (i.e. stress-rupture, dwell low cycle fatigue, etc.) at elevated temperatures, and typically requires a coating (i.e., a low temperature diffused aluminide coating) thereon to protect it from environmental effects. The presence of such coatings can further degrade the notched properties of the Thermo-Span® material, potentially allowing Thermo-Span® components to crack in service. This cracking is typically observed at highly stressed areas where stress concentration characteristics aggravate the material's notch sensitivity, such as at hole locations.
While various methods exist for repairing gas turbine engine components made of traditional mainstay alloys, there are currently no methods available for repairing gas turbine engine components made of Thermo-Span® material. Therefore, damaged Thermo-Span® components must be replaced by an entirely new component, and the damaged Thermo-Span® components are being returned to the manufacturer or set aside until a suitable repair method becomes available for salvaging them. As the number of damaged Thermo-Span® components continues to grow, the costs associated with those damaged components continues to rise as well. As such, it would be very desirable to be able to repair damaged Thermo-Span® gas turbine engine components so that such components could be returned to useful service.